An artificial neural network (hereinafter, simply referred to as a neural network) is an information processing system modeled on a biological neural network. A computer having a higher performance than a conventional Neumann computer is expected to be provided by utilizing the neural network, and in these years, a variety of researches on an neural network constructed over an electronic circuit have been carried out.
In the neural network, units that resemble neurons are connected to each other through units that resemble synapses. By changing the connection strength (in this specification, the connection strength is referred to as a weight coefficient), a variety of input patterns are learned, and pattern recognition, associative storage, or the like can be performed at high speed. Furthermore, Non-Patent Document 1 discloses a technique relating to a chip having a self-learning function with the neural network.